PROJECT SUMMARY In its initial funding period, the ABCD consortium used a rigorous epidemiological approach to recruit a diverse sample of 11,878 9- to 10-year-olds through our 21 research sites, of which 2,136 are twins or triplets. Expert workgroups (WGs) designed protocols using proven methods to assess, scan, and maintain this cohort with very high retention rates. The study complements well validated standardized assessments with novel real-time objective data collected wirelessly in the natural environment to securely capture indices of youth behaviors. These technologies add measurement precision, ecological validity, and an opportunity to reveal previously unknown effects of behavioral, physiological, and environmental factors in the development and fluctuation of substance use, screen media use, mental and physical health concerns, brain development, and their dynamic relationships. Bioassays (e.g., from hair, shed teeth, blood, and oral fluid) provide genome-wide genotyping, pubertal hormones, more precise estimates of exposures to substances of abuse and environmental toxins, and eventually more comprehensive estimates of relevant epigenetic effects. State-of-the-art harmonization methods for MRI and other data enable seamless data integration across sites into an invaluable open-science database that becomes available to the larger scientific community within a year of data collection. The Coordinating Center (CC) met all of its previous aims, and here describes how it will achieve an adjusted set of aims for the next 7 years. Specifically, we describe a flexible organizational framework created for management of the study that relies heavily on cross-disciplinary knowledge and extensive research experience of expert assessment WGs and strategic planning groups, and a dedicated team within the CC, Data Analysis, Informatics and Resource Center (DAIRC), and NIH to coordinate internal and external communications; support and integrate the development and revision of protocols and data quality reviews performed by WGs; establish, monitor, and maintain the standardization of study protocols across the consortium sites; measure and review study progress toward goals for retention, data quality, and scientific impact; based on these metrics, take supportive and corrective action to ensure that the goals are met; manage bioethics policies and consortium interactions with the single IRB (sIRB); promote the professional development of diverse junior investigators; establish a framework to resolve conflicts within the CC or within the wider consortium; and responsibly address any unanticipated scientific, methodological, logistical, or ethical challenges to ensure the study achieves its overarching objectives. We also describe how the CC and DAIRC will together implement quality control procedures to improve data quality across all data types; coordinate data sharing functions with the staff of the NIMH Data Archive; manage a pipeline for enhancing the study with novel assessment technologies; and facilitate rigorous analyses of ABCD data that set new standards for use of data from this powerful, but complex and challenging, high-dimensional study.